We propose to purify the 8 or 9 different messenger RNAs that are present in high abundance in the mouse liver. The purification will involve the use of cDNA coupled to Sephadex or cellulose as an affinity matrix and acrylamide gel electrophoresis. The polypeptides specified by these mRNAs will be identified by translation in a cell-free system. Several aspects of the expression of these sequences will be examined. These include an analysis of the turnover of the mRNAs in the liver. We will also estimate the rates of translation for each of these mRNAs in the liver. We have shown previously that these mRNAs contain a fraction that is represented by multiple copies in the DNA. We intend to analyze the distribution of these repeated DNA transcripts in the mRNAs using a repeated DNA-Sephadex column as a probe. Finally, using hybridization to cDNA we will determine the rates of accumulation of these mRNAs during development to see if several or all of the sequences increase in concentration coordinately.